Due to various factors including degradation of natural environment, gas emission from cars or industrial plants, housing conditions etc., or change of foods, it is said that one out of 3 persons suffers currently from some kind of allergic disease. Especially, food allergy is a harmful immune response induced by an intake of allergy-inducing substances (hereinafter referred to as food allergen) which induces dermatitis, asthma, gastrointestinal impairment, anaphylaxis shock, etc. As the number of patients suffering such food allergy increases, severe problems are arising in the medical field, as well as in food industry. These hazards sometimes lead to death, and it is necessary to take some medical procedures in advance. Thus, necessity to provide information to consumers on a label is increasing, and the Joint FAO/WHO Food Standard Committee has agreed to indicate the content of foods containing 8 types of raw materials known as allergic substances. It was decided that each member country would consider an indication method appropriate to the system of each country (June 1999). In Japan, a labeling method was established for 24 foods, which have actually induced severe allergic symptoms, by taking into account the degree or frequency of health damage in the past (executed from April 2002). Eggs, milks, meats, fishes, shellfishes and mollusks, cereals, beans and nuts, fruits, vegetables, beer yeast, gelatin, etc. are known as foods inducing allergy. Especially, αs1 casein as a main ingredient of milk allergen, β-lactoglobulin as a main ingredient of whey allergen, ovalbumin and ovomucoid as albumen allergens, gliadin as a main ingredient of flour allergen, proteins with a molecular weight of 24 kDa and 78 kDa as main ingredients of buckwheat, or Arah1 as a main ingredient of peanut are known.
Conventionally, as methods for detecting allergens, for example, a method for quantifying immunoglobulin that reacts specifically to allergens (see Japanese Laid-Open Patent Application No. 05-249111), a method for measuring allergen-specific IgE antibody in a sample comprising dissociating an antigen-antibody complex in the sample by acid treatment and the like, and performing neutralization treatment by using alkali according to need (Japanese Laid-Open Patent Application No. 07-140144), etc. are known.
Further, as official methods (KOTEI-HO; Japan) for detecting specified raw materials such as milk, egg, flour, buckwheat, and peanut, an immunological detection method using polyclonal antibodies obtained from heated/non-heated complex antigens (see Japanese Laid-Open Patent Application No. 2003-155297; hereinafter referred to as “commercial KOTEI-HO A”), or an immunological detection method using polyclonal antibodies obtained from purified antigens (herein after referred to as “commercial KOTEI-HO B”) are currently used. These methods are effective for specifically detecting allergens, while they also have many problems. For example, as complex antigens are used in commercial KOTEI-HO A, it is unclear against what the antigen, and the crossing property is high. For example, antigens cannot be identified by immunoblotting, etc. and there is a possibility that non-specific responses increase. On the other hand, in commercial KOTEI-HO B, the specificity of antigens is clear as the antigens have been purified. However, as antibodies prepared by using native antigens are used, the binding-level of antibody is different depending on whether it is native or denatured, which leads to a problem that the quantitative level differs before and after heating, even when the added amount is the same. Especially, as flour is often subjected to severe heating treatment compared to other specified raw materials (eggs, milk, buckwheat, peanut), (for example, bread, fried food, etc.), flour allergens are present in a wide range, from a native state to a denatured state by heating. Therefore, it is necessary to prepare a monoclonal antibody which makes it clear to what stage of allergen the antibody is bound, and to use the antibody according to its property.
Further, for identification and quantitative determination of eggs, a method using a polyclonal antibody using ovomucoid as an index (see for example, Int. Archs. Allergy appl. Immun., 75, 8-15, 1984), or a method using a monoclonal antibody (see for example, Nutr. Sci. Vitaminol. 45, 491-500, 1999) is known. Moreover, an immunological quantitative method has been reported which enables identification and accurate quantitation of egg allergens by determining ovomucoid by discriminating even a denatured state by heating, with the use of a monoclonal antibody which recognizes ovomucoid, wherein the monoclonal antibody reacts with native ovomucoid while not reacting with heat-denatured ovomucoid, or that reacts with heat-denatured ovomucoid while that does not react with native ovomucoid, or that reacts with native ovomucoid and heat-denatured ovomucoid (see for example, Japanese Laid-Open Patent Application No. 2002-253230).